Surface Modification Of Low Density Polyethylene Research Articles

Biostable Fluorine-Containing Coatings on the Surface of Polymers

We considered the formation of the integrated biostable coating on the surface of several polymers using the original gas-phase fluorination technology. The effectiveness of surface modification of low-density polyethylene (LDPE) and polypropylene (PP) was confirmed by corresponding changes in the absorption spectra of infrared radiation with the modified samples. The gas-phase fluorination quality of ultrahigh molecular weight polyethylene (UHMWPE) and nitrile butadiene rubber (NBR) surfaces was evidenced by the results of scanning electron microscopy (SEM) and energy dispersion analysis (EDS). As was shown with the direct measurements of water and ethyleneglycol wetting angles, the properties differences of the polymer materials with modified surfaces from the initial one correlated well with the change in free surface energy induced by the chemical and morphological transformations under the fluorine and oxygen-containing gas mixtures treatment. The developed technique for the bio-contamination degree quantifying, based on the computer analysis of the corresponding images, allowed us to establish that gas-phase fluorination of the surface approximately doubles the time during which the biofouling of LDPE, PP and UHMWPE with the mixed colony of Rivularia and Stigonema Minutum algae occurs under natural conditions. No positive effect from fluorination was observed for NBR, which was explained, from our point of view, by the difference in the mechanisms of biostability for the considered polymer materials.

PLASMA-ETCHING AND MODIFICATION OF POLYETHYLENE FOR IMPROVED SURFACE STRUCTURE, WETTABILITY AND OPTICAL BEHAVIOR

In the present paper, the surface modification of low-density polyethylene (LDPE) polymer is done by plasma-etching to tune its surface structure, wettability and optical behavior to make it useful for technical applications. For this purpose, two gasses (N[Formula: see text] and (O[Formula: see text] are used as the discharge precursors in a home-built plasma reactor. The plasma-treated LDPE surface etch-rate (control other surface properties) is high at the beginning and slows down as the treatment time increases due to surface restructuring. The etched surfaces are analyzed by scanning electron microscopy (SEM), which indicate greater surface changes due to O2plasma compared to that of N2. Also, the surface hardness is slightly low at the first treatment time and increases rapidly at higher exposure durations. Besides, the friction coefficient is significantly changed by plasma treatment, suggesting the formation of cohesive surface skin. The obtained X-ray diffraction (XRD) patterns show that the plasma-treated LDPE samples suffer disordering and structural changes which increase with raising the treatment duration. Surface restructuring is attributed to the combined effects of active species (from plasma) bombardments and surface oxidation. Also, the surface chemistry changes are evaluated using attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy which reveals chain scission after N2plasma treatment. Whereas, the O2plasma-treated samples suffer surface oxidation and formation of polar groups which offer some surface oxidation coatings. Furthermore, the surface wettability has been determined by the sessile drop method and shows enhancement upon plasma treatment due to the combined influence of surface chemistry and morphology. Also, the surface free energy (SFE) and adhesion are found to increase with the plasma exposure time due to surface activation. The optical behavior of LDPE is studied using ultraviolet–visible (UV–Vis) spectrophotometer which indicates that the optical bandgap performance depends on the amorphous or crystalline nature of the polymer. Also, the conjugated carbon atoms were examined and correlated to the reduced bandgap. In conclusion, the studied home-built glow discharge plasma reactor could be utilized efficiently to tune polymer surface properties to be used in high technology applications.

Surface modification of low-density polyethylene with poly(2-ethyl-2-oxazoline) using a low-pressure plasma treatment

Low-density polyethylene (LDPE) is a suitable polymer for biomedical applications due to its good physiochemical properties, but its insufficient biocompatibility is often an issue. Therefore, biocompatible substances such as those based on 2-ethyl-2-oxazoline seem to be a good choice to increase the LDPE biocompatibility. In this work, the surface modification of LDPE with poly(2-ethyl-2-oxazoline) with two different end-groups was investigated. This modification led to the improvement of surface and adhesion properties, which were investigated by several analytical methods. The low-temperature plasma treatment of the LDPE surface was sufficient to create binding sites for the permanent attachment of poly(2ethyl-2-oxazoline) chains. This was confirmed by infrared spectroscopy and X-Ray photoelectron spectroscopy. It was found that the polymer containing the acrylic end-group was well attached to the LDPE surface.

A Novel Two-Step Procedure for Plasma Surface Modification of Low-Density Polyethylene for Improved Drug Adhesion in Intra Uterine Devices (IUDs)

The Intrauterine Devices (IUDs) are unable to prevent STDs (Sexually Transmitted Diseases) and PIDs (Pelvic Inflammatory Diseases) which seriously restricts their usage. RISUG® (Reversible Inhibition of Sperm under Guidance), a potent spermicidal and antimicrobial drug is being coated over copper-T frame (made of polyethylene) by exposing it to vacuum plasma treatment twice to increase the adhesion property of polyethylene. First, the polyethylene alone is exposed to certain process conditions of RF (radiofrequency) plasma which increases the surface roughness by creating micro-and nano-pores (as indicated by scanning electron microscopy and atomic force microscopy). Thereafter RISUG® is smeared over the polyethylene of copper-T frame and subjected to the same plasma treatment again. The second plasma treatment causes a "micro-hammering" effect, pushing the drug in the pores and pits formed by the first plasma treatment, resulting in improved bonding. The present study shows that RF plasma treatment alters the surface properties of the copper-T frame without affecting its mechanical properties or primary fabrication.

Surface Modification of Low-Density Polyethylene Films via Photografting Polymerization Technique

Surface modification of low-density polyethylene (LDPE) films was carried out via a novel photografting polymerization technique with acrylamide (AAm) as the monomer. The photografting polymerization can be achieved via one-step method and two-step method. The photografting polymerization reactivity of AAm was examined with benzophenone (BP) as the photoinitiator and low-density polyethylene (LDPE) film as the substrate with “sandwich” assembly. Moreover, the occurrence and evolution of grafting polymerization of AAm on the substrate was demonstrated XPS analysis and SEM pictures.

Surface Modification of Low-Density Polyethylene by Inductively Coupled Argon Plasma

The surface chemistry and nanotopography of low-density polyethylene (LDPE) were modified by downstream, inductively coupled, radio frequency (rf) Ar plasma without inducing surface damage. The extent of surface modification was controlled by the applied ion energy fluence, determined from the plasma ion density measured with a Langmuir probe. The treated LDPE surfaces were characterized by atomic force microscope (AFM) imaging, contact angle measurements, and X-ray photoelectron spectroscopy (XPS). Analysis of AFM surface images confirmed that topography changes occurred at the nanoscale and that surface damage was insignificant. Contact angle measurements demonstrated an enhancement of the surface hydrophilicity with the increase of the plasma power. XPS results showed surface chemistry changes involving the development of different carbon-oxygen functionalities that increased the surface hydrophilicity. Physical and chemical surface modification was achieved under conditions conducive to high-density inductively coupled rf plasma.

Surface modification of LDPE by a DC corona discharge generated in a point-to-grid system: the influence of geometric parameters of the system on modification power

We examined the influence of the geometric parameters of the system on the modification power as determined by the contact angle on the surface of the treated low-density polyethylene (LDPE). We have found that (1) with a constant electric energy to generate a corona discharge, the modification power decreases as the distance from the center of surface (the point on the film immediately below the point electrode) increases and that the corona discharge in a point-to-grid system can modify the film surface over a wider area than in a point-to-LDPE system without grid; (2) with a constant discharge current, the modification power on the center of surface decreases when the point-to-grid gap in negative corona treatment increases, but increases in positive corona treatment; (3) the modification power compared to the electric energy used to generate a corona discharge (the yield) is inversely proportional to the point-to-grid gap. However, in a positive corona discharge, the yield did not reach zero when the point-to-grid gap was extrapolated to infinity, possibly because the streamer reduces the effective point-to-grid gap and produces neutral activated species along the streamer; and (4) in a negative corona, the modification power as measured by the temperature increases at the plain electrode (anode) and varies with the energy dissipated by neutral activated species.

Surface modification of polymers for adhesion enhancement

Surface modification of low-density polyethylene (LDPE) and polytetrafluoroethylene (PTFE) films via graft copolymerization with acrylic acid (AAc), Na salt of styrenesulfonic acid (NaSS), N,N-dimethylacrylamide (DMAA), 2-(dimethylamino)ethyl methacrylate (DMAEMA), glycidyl methacrylate (GMA), acrylamide (AAm) and 3-dimethyl(methacryloylethyl) ammonium propanesulfonate (DMAPS) was carried out for adhesion improvements. The surface microstructure and composition of the modified film surfaces were studied by angle-resolved X-ray photoelectron spectroscopy (XPS). It was demonstrated that the graft-modified LDPE and PTFE films are capable of exhibiting adhesive-free adhesion or auto-adhesion. The GMA graft copolymerized PTFE surfaces adhere strongly to one another when brought into direct contact and cured (i) in the presence of an epoxy adhesive and (ii) in the presence of a diamine curing agent alone. It was further demonstrated that the ozone-pretreated LDPE films and the Ar plasma pretreated PTFE films readily undergo photografting or thermal grafting with concurrent lamination when lapped together in the presence of a small quantity of the monomer solution. The simultaneous graft copolymerization and lamination process can be carried out under atmospheric conditions and in the complete absence of an added initiator or system degassing. Copyright © 1999 John Wiley & Sons, Ltd.

Surface Modification of Low-Density Polyethylene Films by UV-Induced Graft Copolymerization and Its Relevance to Photolamination

Surface modification of ozone-pretreated low-density polyethylene (LDPE) films were carried out via a novel technique of UV-induced graft copolymerization with acrylamide (AAm), Na salt of styrenesulfonic acid (NaSS), 3-dimethyl(methacryloylethyl)ammonium propanesulfonate (DMAPS), acrylic acid (AAc), N,N-dimethylacrylamide (DMAA), and 2-(dimethylamino)ethyl methacrylate (DMAEMA) under atmospheric conditions and in the complete absence of an added initiator or oxygen scavenger. Photografting with concurrent photolamination in assemblies containing a monomer solution sandwiched between two LDPE films was demonstrated. The chemical composition and microstructure of the graft copolymerized surfaces were studied by angle-resolved X-ray photoelectron spectroscopy. For LDPE films with high graft concentrations, such as those graft copolymerized with AAm, DMAA, and DMAEMA, surface chain rearrangement to form a stratified surface microstructure with a higher substrate to graft chain ratio at the outermost surface ...

Surface modification of polyethylene film by liquid phase photograft polymerization

The surface modification of low-density polyethylene(PE) by liquid phase photograft polymerization with acrylic acid(AA), acrylamide(AM) and glycidyl methacrylate(GMA) was described. The grafting of AA and AM was proved and characterized by electron spectroscopy for chemical analysis(ESCA). It was found that fully hydrophilic surface can be obtained in very short irradiation time. With ESCA and attenuated total reflection infrared spectroscopy(ATR-IR), it can be confirmed that bifunctional monomer GMA was grafted onto the PE film surface. Through further reaction with GMA grafted film, heparin and protamine were immobilized onto the grafted film surface.

The surface modification of polyethylene by solution‐phase photochemical grafting using short irradiation times

AbstractThe surface modification of low‐density polyethylene by solution‐phase photochemical grafting with acrylic acid and acrylamide is described. After irradiation for 3 min, the contact angles of the modified surfaces with water were ca. 20, 30, and 40°C and ca. 40, 40, and 80°C for grafting solutions containing 2M, 1M, and 0.1M of acrylamide and acrylic acid respectively. X‐Ray photoelectron spectroscopy (XPS) and attenuated total reflectance infrared spectroscopy (ATRIR) of the modified polyethylene surfaces were consistent with the presence of grafts of polyacrylamide or poly(acrylic acid). Grafting using low concentrations of monomers, that is, 0.1M, resulted in a small, 20° decrease in contact angle for grafting with acrylic acid but a larger, 60°C decrease for acrylamide. © 1994 John Wiley & Sons, Inc.